The inlet casing for an industrial turbo-machine may be required to serve two functions which can be to guide fluid into the turbo-machine and to support the rotor bearings. The common material chosen for this casing is sand cast SG-Iron (SG: spheroidal graphite) which combines the feature of required low temperature ductility with relatively low cost. The draw back of this material and production method is high surface roughness and poor tolerance control especially in the fluid washed area. These causes high scrap and rework costs and potential performance loss.
“SG-Iron” is an abbreviation for Spheroidal Graphite Cast Iron. As the name implies, graphite is present in spheroidal form instead of flakes and compared with Grey Cast Iron it has higher mechanical strength, ductility and increased shock resistance.